1 Field of the Invention
This invention relates to a shutter release mechanism for cameras employing an electrically controlled shutter, and more particularly to a release mechanism that insures shutter release only after the electric circuit becomes stable and insures opening of the power switch contacts if shutter release operation ceases prior to the shutter itself starting to move.
2. Description of the Prior Art
In cameras employing an electric shutter, it is desirable to prevent the waste of electrical power as much as possible. Therefore, the time during which the power switch is closed and the shutter maintained open under control of the electrical circuit should preferably be as short as possible when taking a picture.
Shutter release mechanisms employed in such cameras allow this power switch to be closed and the shutter operating member to be actuated, that is, shifted from shutter non-operating or latching position to shutter operating or release position upon movement of a latching member which is manually shifted by depression of a shutter button.
Although the switch closing time is preferably short, it is desirable that the switch contacts close in the early stage of the shutter release operation so that the shutter itself is released only after the electric circuit becomes stable which occurs shortly after connection of the power source to the circuit components. Further, it is desired that the closed switch should open without fail even when the shutter release is stopped after initiation during the initial stage of release operation if shutter release ceases prior to the shutter itself starting to move. Further, once the shutter itself has started to move from closed to open position, it is desired that the power switch be maintained closed until shutter release is completed.
The present invention satisfies the above requirements by way of a simple and effective construction which insures positive operation at each time of depression of the shutter button.
In accordance with the present invention, the power switch is immediately closed upon the depression of the shutter button, and the shutter operating member is actuated by continued movement of the release member by contact of the shutter button with a time delay between closure of the power switch contacts and positive movement of an associated latching member to unlatch the shutter operating member. Further, in accordance with the present invention, the release member is held in the shutter release position by movement of the shutter operating member to shutter operating position to maintain the switch contacts closed until the shutter release operation is completed.
Specifically, the release mechanism of the present invention includes a pivotable shutter operating member movable between shutter latching position and shutter release position. First means spring biases the shutter operating member towards the shutter release position. A latching member in juxtaposition to said shutter operating member and pivotable between latch and unlatch positions has an end portion engageable with said a shutter operating member to maintain said shutter operating member in shutter latching position against the biasing force of said spring means. Second spring biasing means, spring biases the latching member towards latching position. A release member is pivotably mounted common with said latching member, is spring biased towards engagement with said latching member, and is operatively positioned with respect to a power supply switch for supplying power to the electrical circuit and controlling the electric shutter so as to normally maintain said switch contacts thereof in open position. The release member is pivotably mounted relative to the shutter latching member in a manner to permit limited movement of the release member relative to the latching member to allow the release member to close the switch contacts prior to driving the latching member against the second spring biasing means. Movement of a push button or a push button interlocking member causes the latching member to rotate about the common pivot axis, disengaging the latching member from the shutter operating member and permitting the shutter operating member to pivot under the bias of the first biasing means from shutter latching position to shutter release position. Means responsive to movement of the latching member to unlatch position and constituting engagement of the shutter operating member with another portion of the latching member positively maintains the release member in release position to insure continued closure of the power switch contacts.